Oil tank and system



Feb. 5, l1952 Filed April 30, 1945 A. c. HOFFMAN ETAL 2,584,877

OIL. TANK AND SYSTEM 5 Sheets-Sheet l ou. COOLER Walle/f h'. eddes dames olcoii Gorneu Feb. 5, 1952 A. C. HOFFMAN ET AL OIL TANK AND SYSTEM 5 Sheets-Sheet 2 Filed April so, 1945 l mw MNA@ E m mfmmm f Ma 6 w. Mam m Ww@ mw mm /S Feb. s, 1952 Filed April 30, 1945 A. C. HOFFMAN ET AL OIL TANK AND SYSTEM 5 shets-sheet s dal .-3

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` all orneq Feb- 5, 1952 A. c. HOFFMAN :a1-Al.v 2,584,877

OIL TANK AND SYSTEM Filed April so, 1945 `5 Sheets-sheet 4 c l l l 1 v l n f n r l l 1 l 1 l a l l l l 1 n Waite/'fl'. Geddes @ld/2m Olcolz @H eu Patented Feb. 5, 1952 signorst'o United' A craft` Products, Inc., Day'- tbligfohmfacoro ation oQh'io ApplicationiApriliSil, 1945,y SerialgNo. 591,182'. nomine, (erige- 195) This invention relates to apparatus foin-.egu-` latingy the. condition of. oilsuppliedto an aircraft. engine. or. the like for lubricating; purposes..

. In general, the, object. of` the invention'. is to, supplyto the engine, oil whichL is conditioned. for'v effective-lubrication at all-.temperaturesanclatlalli altitudes. of ilight,. and4 to remove from the oila discharged bythe engine functionallcharacteristicsi of-an objectionable kind:

Aircraft design of recent. effort has. been4 di,- rected to improvemeni'.--ot` operation.A at., high. alti;- tude andz under conditions ofA low. temperature. The need for major modification; offthe engine lubrication system. has i been particularly: felt,. andi correctivemeasuresihave beenappliediinuthe' forma, ot oil. temperature. regulators, deaerators.- and; diluting: means.v Oil temperature regulators: hav..- ing: quick warm-upl and anti.-congealingfcl1ar acteristieslv are successfully` employed but.I the. problem. of. complete oi'lf, conditioning isi not; tullyf answered by limiting. the maximum.v oil; temperature to. a predetermined value., Deaenators. off thef kind heretofore known add, ai newr unit ta the lubricationsystem andi often are. Objectiona.. blev as causing. an undesirably high, pressure drop. The: addition of a. diluentto.. the oil.. to-` lower. its-v viscosity and, thereby insure. oiuicllz enginestart under, V.cold clima/ticv conditions;l has prox/:edi a.- process of merit` but hesfini, the neet.;-,biong-liiion; certain. deleterious effects. such as'. violent; boil; ine-in, the oilI tank (resulting in.-r Spewine and1 loess, ofE oil) and the supplying of a.1ubrioanttotli e, engineioo low in iiieeoeiiy. forfpioperf lubrioeiion.

The present invention enooinnoeeee. all. known liibiieeiion, problems., end iief ebbioaolif, ioiveiflj modiiieaiiori of the lubrieeiion einem has be:- eun. ei the eoiiree of oil Supply. namely the olle tank. It is contemplated` that thetank as,

sociated parts` shall function:V

` (a) Tofsupply' an adequate. volume of oil to the engine, With substantially alltlieJ oil in the` tank being electively andv quickly conditioned for. ilow.

(b)V To deaeratethe oil.

(o) To eect dilution oi." a, portion of the oil in the system and to segregate the. diluted' oil' from the' non-'diluted'. oil.

(d) To regulate the temperature. of*` tlie, oil at. temperature values lower. than themagiinurn set by the. oil ternperaturev regulator.

(e). To prevent. the combined eieots, of. d ilution and` rapid'` Wann-up from decreasing, the, lubricant viscosity to an objectionably, low level".

A further object of' the'. invention to ine, eoriioreio elle. engine liibrieetion. einem@ 2 reservoir. from, Whieb Ileisl, elibeeoilenily.. nlaeeo underv pressure, be supplied tothe, propeller featlerngmechanisni of the. aircraft, ,'suc'li. reser-` Voir.v tok. benornially si'loplfied with diluted oil-but,-

eiieble ibejbroeeee of; dilution oi .ille liibrieeiine.; o il ,be eoeomnenied. by, e ioreedfloiv; ofthe eine ellleiiiie .oilibioileiiiibe oil-` temperature regu@ 1oio1.,\ibeieby. io eool the oileno'inhibieii rabid.. deeline of rieoosiix; endbollfoii; of the dilueni.

Qihev obleoieend structurel detailsl of the veililon. will @meer rfrom ille following descrip: tiene when. reeel: Connection with the Y'ioeorn.-y o.oiiyine drewinee. wherein: i

li'e.- l-,is e. diagrorriof an aircraft engine, lubrioeliion. eyeieni and engine fuel... system, in ac.: oordenee with the present. invention;

Fie; 2*.is: a view in.. longitudinal, section. partly diagrammatic oftheioil tank. including a. themiof. steil/,ioelly..l controlledt flow; sequence. valve shown, as. itis:C positioned.l during,i Warm-up` of the, engine; o1:v when theloil isi colds.

Fig.vr 3y is;4 a. View.. of. the. oil tanlo inv cross, section.. taken. substantially along, the. line, 3-.3 of Fig.. 2;.

Figg. 4 is a.:V fragmentary view` of; the, oil, .tank,. showing the sequence, valve as. it appears. during: a. late; stage the warmfupiperiod;

l'ig. 5; is a.: view. similar-toFi'g. 4showing the: sequence/valve asitlappears when the;A oi1,;ishot;

Eig',A 6 is; a vieri!l similar.. to Eig. 5,.showing the sequence valvey as it appears; during the dilution;

PYOGGSS; 1

Fig, 7; is a, detail view, in, perspective, ofi an ele-I,

.ment Glle Sequencevalye., assembly;v

Fie@y itisl adieerain Similar, toFia 1,; showing a, modification, of; the invention aiecting the oil cooler;- andV Fig; 9 isl a fr.oeinbiliari'` view; in longitudinal Seoiionlof theoilooolenaslinodied accordance Withthe. arrangement of Fig.. il.

the diee'ieni. combining Fig ,1 an aircraft engine ie. indicate@ et L0. emilie carburetor ei..- il. ibegeebiiieior beine eiiniblied.- with liquid fuel eeen ee-eeeoliiie bie,Y e' eenden# leeiiiba fibbifuel tank. |3`. A pump., I4.. is. disposedinthe line!x i2? ariq'jcauses tilefeitqmw tothe engine iin'det pressure, wliubricating. o il is drected'totheengiiie by way of. a conduit |,5fconnected at its opposite endsE to. the engine andf to an oil tank l'if. An engine. driven puin-p Il' isA arranged in tHe line lifadjaent. thev engine Ill! whereby oil. may be.

die. iioifilie'ieiib'f ofridiore'ed under' Dreef Sii. io. tbe: eneineb-eeiinee. end-embers eflibii- 3 cation. After passing through the engine the oil may collect in a sump or the like from which it is drained by another engine driven pump I8 and returned thereby to tank I6. The return oil conduit consists of a line I9 connecting the pump I8 to the inlet of an oil cooler 2I, and a line 22 connecting the outlet of the oil cooler to the oil tank I6. During operation of the engine I the pumps I1 and I8 function continuously, the former to draw oil from the tank I6 and deliver it to the engine and the latter to take the oil from the engine and return it by way of the oil cooler 2| to the tank for re-use.

Referring to Figs. 2 and 3, the oil tank I6 comprises an outer shell 23 which may assume different shapes and sizes in accordance with the capacity of the system and with the location in the aircraft in which the tank is to be installed. The present illustration is in part diagrammatic, and shows the tank as a one-piece sheet metal container generally rectangular in form. The tank has alternative inlets 24 and 25 positioned adjacent one another on the upper side of the tank, and a single outlet 26 on the lower side of the tank. The engine supply conduit I is connected to the tank at the outlet 26. Vertically disposed within the tank shell 23 and extending between the inlet 25 and outlet 26 is an inner tank compartment or hopper 21. The hopper 21 comprises a generally cylindrical body portion 28 having one end resting on the lower side of the tank in a position surrounding outlet 26, and further comprises a flared upper end 29 constituting an overflow protection. Extending through the inlet 25 downward into the tubular portion 28 of hopper 21 is an inlet conduit 3I.`

There further may be arranged within the tubular portion 28 of hopper 21, in a position surrounding conduit 3 I, a cylinder 32. The cylinder 32 is closed at its lower end and open at its upper end, whereby the oil from conduit 3l is directed` first to the lower end of the cylinder and then compelled to flow upward along the outside of the conduit to the open end of the cylinder where it overflows into the hopper 21 and passes to the outlet 26. A curved baie 33 is fastened to the conduit 3l immediately above the open end of cylinder 32 in order that displaced oil may be' The funcdeflected downward in the hopper 21. tion of cylinder 32 is as a reservoir for supplying liquid to the propeller feathering mechanism. It will be observed that the lower end of the reservoir 32 opens into a conduit 34 which is passed through the hopper 21 and out of the tank shell 23. Referring again to the diagram of Fig. 1, it will seen that conduit 34 leads to a hydraulic cylinder 35 constituting the means for feathering the propeller 36. The actual means for turning the propeller to a feathered position forms no part of this invention, and it will be sufcient to say that a selectively operable pump 31 is disposed in line 34, which pump when operated draws oil from reservoir 32 by way of conduit 34 and directs it under pressure to the cylinder 35 where feathering is accomplished in a known manner. desirable that the oil in line 34 be maintained inA a free-flowing condition. To this end, as will hereinafter appear, the feathering line is diluted as a part of the general dilution process.

Within the shell 23 of the oil tank I6 is a conduit 38 having one end registering with the tank inlet 24 and discharging at'its other end into a manifold 39. As may be seen in Fig. 3, the manifold 39 is located near one end of the tank and It is, however, important and 4 adjacent the upper side thereof, and extends as a closed cylinder for approximately the full width of the tank. A longitudinally elongated slot or opening 4I is formed in the manifold 39 from which the oil flows in a wide shallow stream. Beneath the manifold 39 is a bafe 42 which touches and is secured to three sides of the shell 23 and has one end terminating a short distance from that end of the tank opposite the manifold 39. A passage 43 is defined between the free end of baille 42 and the adjacent end of the tank. Beneath the baffle 42 is another baflie 44, similarly constructed but oppositely arranged to define a passage 45 around its end at that end of the tank opposite passage 43. While the baffles 42 and 44 are secured to the shell 23, they preferably are fastened by means not constituting a continuous seal, in order that air may not be trapped beneath the bailles. Beneath the baille 44 is another baille 46 which is secured to the hopper 21, with its ends terminating short of the walls of the shell. The several baffles 42, 44 and 46 have aligned openings therein to accommodate the tubular hopper 21. The baffles 42 and 43 incline downwardly within the tank, the angle of inclination being gradual so as to produce a relatively slow flow of the oil from the manifold 39 to the bottom of the tank. Thus the oil entering the tank by way of inlet 24 passes through conduit 38 to the manifold 39 from which it emerges as a wide at stream onto the baille 42 along which it flows toward the opposite end of the tank and through passage 43 onto the lower baille 44. The oil stream continues along baie 44 to the other end of the tank and through passage 45 to the bottom of the tank where it is compelled by baffle 46 to pass toward the outlet 26. The oil so flowing reaches outlet 26 through a series of radial ports 41 in the lower end of the tubular portion 28 of hopper 21. The ports 41 are controlled by flapvalves 48 hinged to the interior of the hopper and carrying weights 49 which tend to hold the valves closed until a definite opposing pressure is applied.

The combination of the manifold 39 and inclined bailles 42 and 44 is designed to prevent uneven turbulent flow Within the tank, and in so acting to produce an added feature of advan-v tage, namely the release of entrained air from the oil. A weil-known disability of aircraft engine lubrication systems, which conventionally are of the dry sump type, is that the high capacity scavenger pump, indicated at I8 in Fig. 1, operates at times to pump air into the system. The air Vmingles intimately with the oil, particularly under conditions of high temperature, and impairs lubrication. As a deaerating provision the tank has, in addition to the bales 42 and 44, foam vents 5I and 52 extending downward into the tank. The upper end of each of the vents 5I and 52 projects through a perforated tray 53 which defines within the tank beneath the inlets 24 and 25 a space 54 communicated to the exterior of the tank through a conduit` 55. The conduit 55, may, as is indicated in Fig. l, return to the engine sump or it may simply discharge overboard of the aircraft. The lower end of the vent 5I passes through the baffle 42 near the higher end thereof and terminates immediately beneath that baffle. The vent 52, which is located at the opposite end of the tank, extends through baffle 42 and baffle 44, terminating immediately beneath baille 44 at thehigher end thereof. The low velocity flow ofthe oil along the baffles 42 and 44, and the'shallowness of the owing stream, perassieme mits :a `separation -of 'the air vfrom .the .oil inthe form of :air bubbles for 4as foam. Bubbles and foam released -irom 4.the `oil during .its ow .along baille 42Lmay rise .in the tank .and pass through the perforatiens .in `tray 63 into the vented space 54.- .As the .oil makes "an abrupt .turn .atthe end. of each ba-le, .foam tends to .collectrbeneath the: raised vends `of the baffles randis permitted to escape therefrom by `way of `.the vents 5| .and-1.52. After rising to the top ofthe vents .5| and 52 the foam .lies vin a quiescent conditionyivithin the space .5.4 whereupon the Abubbles may coalesce and break, the. liquid oil .dropping down through the. perforations in tray 53 to the main Vbody of oil. The lair releasedirom the breaking bubbles ,passes from :the tank Vby Way of .conduit 55. Effective deaeration of .the `oil .therefore Vis accomplished `by a combination .of .means producing :a .circuitous iloW paththrough .the tank, .an absence `of turbulence .and shallowness .of the flowing .oil.stream. The size andshape of .the oil .tank determinesthe number, position and size of the baiiies and foam vents required for .best deaeration.

While the baiiles v42, 44 and 46 are shown as made of ilat sheet metal stock, they .may be corrugated to induce a more rapidreleaseof entrained air. Also, some or all of `the baiiles maybe com.

structed of `vvire mesh screen and .so function as filters to .remove foreign particles .from 'the oil. The large combined surface area of the ibaiiies makes .possi-ble a highly eiective lterand obviates the need for conventional filter .accessories which create a high pressure drop `and are lim--4 ited .insurface .in proportion .to their. size.

Alternative use is made cf the. .tank inlets .i4n

and in order that the oil returning fromthe engine may be directed .at one .time through the short path represented by the .hopper 21, at another time through the long path represented by the baied fpassageway in the main tank, and Aat still another time through both paths. There is mounted on the tank I6 a flange oriitting 5.6. having openings 51 and58 therein `respectively overlying the tank inlets 24 .and 25. Opening .5.8,

may receive with a press fit the upper. end of Mounted `cn the fitting 56 is .a `se.

conduit 3|. quence valve .assemblyJ .including a housing V59. formed with internal Walls deiining .a vcentral inlet chamber 6| and oppositely.disposedoutlet.. chambers 62 and 63. A-s shown in Fig. 3, the` central chamber 6| constitutes the discharge end. of conduit 22 by which oil returningr from the. eng-ine is conveyed to the tank. Chamber 62 overlies opening 51 in ttng-E and so communie catesgthrough inlet 24 -With conduit `38 .and the long path through the tank. Chamber63 .overlies opening 58 in tting 56 and socommunicates with conduit 3| and the short path through the tank. Chamber 6| is connected to chamber 62 by a port 64 and is connected to chamberv 63,by. a port 65. Within the housing 59 isa valve. assembly comprising opposed valves 66 and .67; respectively controlling ports 6 4 and65. As may be best seen in Fig. 4, the valve assembly includes a body A68 having a vertical wall GBadeIining a chamber 69, and having arearwardly extending skirted portion 1| which is enlarged at its end to form the valve 61. The valve 61 controls ow through the port 65 by moving partly or wholly,l within the port. The left hand or front end. of the .chamber 69 in body 68 is closed by adiaphragm 12, in front of which is a connector .plug 13 of rubber or rubber likematerial contained in a body extension 14. In advance of the .plug 13- isapiston 15 slidable upon a pin '16 ,securedina- 6* plate 1J which serves :to close .one fend fof ithe. housing 59. The :piston 1.5 is slidablevzithin |the: extension .14 which'functions as aguide therefor., TheV `'valve 66-is mountedon the .body r68 fandis4 engageable with the `.end of a cylindrical `praticotion 18 of the. closure plate 1.1, the projection .118: extending into the housing .59 within the port66. The valve assembly zisihermallyfactuated, there being within the chamber .69 .of body 6.8 an anion.. phous .material 19 .having the property .of ,expan-4 sion under the addition @of heat. According. to. the .construction .and arrangement .of the valve. parts, expansionpf .the material 1.9 .is transmitted; through the diaphragm 12 and connector plug J8 to .the piston 1.5, and tends to .press .the-piston against the .pin 16.. The .pin 16 being fixed,- .a reactiveforce isapplied to the body .6,8 vand :asso-. ciated parts tending to move .the valve 66 away: from port .64 and to move. the valve .61 toward port v.65. When `the thermal .substance `19v :cools itis recompressed, Aand the body 68 returned to its starting position, Lby aspring 8|. .'Ihespring 8|A surrounds asleeve 82 having .one .end within the skirt 1| and formed .with circumferentially spaced lugs or .projections 82a .(see Fig. .7) .seated on -the'vvall 68a of body 68. .A radial iiange .83.;is formed von the sleeve 82 at the ybase of projections 82a. and contacts the inner wall of .skirt 1|. The. sleeve 3.2 extends through port .65 .into .chamber 63, and spring 8| is interposed between thenange. 83 and the wall of body 59. The freeouter .end of sleeve 82 receives one end of a bushing .84, the opposite end of which is formed .with a .flange accommodated in arecess in .the wall ofbody 5.8 and serving as a base for the spring 8|.

VThe valve body 68 .and valves .6.6 and 61 .are ar ranged within inlet chamber 6| so that oil entering the chamber .6| may :dow around the valve assembly and by .a proceses of heat conduction induce in the thermal substancec 19 an action :ap. propriete to the temperature of the oil. `Inorder that .the oil may not heat the substance .19 .too quickly a hood or shroud 85 is vmounted. .on .the body 68 in spaced relation to that partfdening chamber 69. In accordance with the varying temperature of the oil, therefore, the valve .assembly is caused to move in such manner as to direct theoil entering .chamber 6| either .to chamber 62 or to chamber 63. Also .it vvill be noted. that the valve assembly may assume .an .intere mediate position in which theow issplit, iiowing! in part to chamber -62 .andin part to .'chamber. The oil in chamber 62 is permitted to lpass -to .the tank inlet 24 by .Way of a series of openings 86 in the projectingportion 18. of` closure .plate 1.1.. ,In general, the .operation of .the valve assembly Ais such that when .the oil returned vfrom the engine is cold, or Abelow .a lpredetermined temperature'- value., `the, parts assume under the urgingof spring 8| a positionlike that shown .in Fig. 2. 'Thus' valve .66 is held closed within a portllfandflow is denied .to tank inlet 24, while port 65 is open permitting the oil to pass therethrough and by' way of conduit 3| .to the hopper 21. A quantity of oilless than .that available in the systemthereby is circulated. As -the .circulating oil-am quires .a higher temperature valuefsuch tempera--4 ture change is .reected in expansion of the thermal vsubstance 19 resulting in motion of the valve assembly to .Withdraw valve 66 fromclosed position and to move valve 61 toward port 66.- As vis indicated in Fig. 4, Aduring 'an intermediate range 'of Itemperature values the oil ow lwill Ibe divided between the ports 64 and 65, both of' which are. open. .As the .oil temperature :con-

tinue's to increase, the motion of the valve 61 toward closed position will continue until port 65 is blocked (Fig. so preventing further flow through the tank by Way of hopper 21. Substantially all the oil returned from the engine then mustpass by way of port 64 to inlet 24 vand the long path through the tank. It will be observed that rthe manner of closing port 65 by valve 61 is such that in the event of excessive pressure in the system, as may result from a blocking of the flow in the main body of the tank, valve 61 may move under pressure through and beyond port 65 to permit a by-passing flow of the oil to the tank by way of hopper 21.

According to the present invention the introduction of a diluent into the system is accomplished through the valve housing 59, and is accomplished in such manner that irrespective of the oil temperature the flow through the tank during dilution will be by way of the hopper 21. This'is desirable in the interests of economy of time and of diluent. The diluent employed may, as is indicated in Fig. l, be gasoline drawn from the fuel tank I3. A conduit 81 is connected at one end to the fuel line l2 on the pressure side of pump I4 and is connected at its other end to the tank valve housing 59. Interposed in the conduit 81 is an electrically actuated solenoid unit 88 operable in a well-known manner when energized to open a valve to permit flow through the line 81 and operable when de-energized to close the valve and deny ow through the conduit. The solenoid 88 is disposed in an electrical system comprising a battery 89 from which extends a positive lead 9| and a negative lead 92 establishlng a circuit through the solenoid 88. A switch 93 is disposed in the line 92 and is movable to open and close the circuit in the electrical system whereby to energize and de-energize the solenoid 88. u

Referring to Fig. 6, the conduit 81 is received in a threaded opening 94 in the closed end of valve housing 59. The opening 94 registers with the bushing 84 of the sequence valve assemblyl so that diluent entering the housing by way of conduit 81 is conducted through the bushing 84 and through the sleeve 82 to the rear of body 68. From the interior of sleeve 82 the diluent may flow past the projecting lugs 82a beneath the annular flange 83 and through a series of ports 95 in the body skirt 1I to the space between body 68 and the shroud or hood 85. Escape from the hood 85 is provided by ports 96 therein through which the diluent may ow to chamber 6l and thence by way of port 65 to conduit 3l and the hopper 21. The diluent being considerably lower in temperature than the engine oil, and further having a cooling eect by reason of its high rate of evaporation, the effect gained is a chilling of the ther- Y mal substance 19 to allow the valve assembly to move by the action of spring 8|l to a position opening port 65. Accordingly, during dilution the oil flow through the tank is by Way of hopper 21. As the oil flows, the diluent intermingles therewith and produces a diluted mixture of lesser density than oil alone and one which is less susceptible to congelation. The quantity of liquid flowing through the hopper 21 is increased by addition of the diluent but overflow into the main tank is prevented by the flared extension 29 of the hopper.

As is illustrated in Fig. 6, motion of the valve assembly in response to the cooling eiect of diluent introduced into the system, in addition to opening port 65, causes valve 66 to close- Dort 64.

Therefore, circulation of the oil through the system is accomplished independently of the main body of oil in the tank. In order to prevent complete congelation in the manifold and lines leading to the main tank under these circumstances there is provided in the valve 66 a small diameter port 91. Through the port 91 a small amount of diluent and diluted oil may pass to the tank inlet 24 and fill the conduit 38 and manifold 39.

Further, and in connection with the operation of feathering the propeller, there is provided in the housing body 59 a small diameter port 88 connecting the inlet chamber. 6I and the chamber 63 communicating with hopper 21. By reason of port 98 a continuous flow of oil to the reservoir 32 is permitted. In this manner should the propeller be feathered while the sequence valve assembly is in position denying flow to the reservoir 32 by way of port 65, the reservoir may be relled by flow through port 98, and the feathering system so conditioned for a second operation.

Additionally. since the function of the tank is tov compel dilution of the system by way of the hopper 21, during the dilution process the feathering line 34 may be lled with diluted oil by exercising the feathering pump 31. The arrangement of the reservoir 32 in the dilution path makes possible a further feature of advantage. Should the oil supply of an engine be exhausted, or inadequate to accomplish feathering, the pilot may close the dilution control switch 93 to open solenoid valve 88 and turn on the fuel boost pump, thereby filling the reservoir 32 with diluent. It will be understood that all the feathering apparatus here disclosed, including reservoir 32, is used primarily with engines of a multi-engine aircraft. In an installation for a single engine aircraft. the reservoir 32 may be omitted from the tank whereupon conduit 3l will discharge directly into hopper 21 without change in the operation of the system.

It may in some instances be desirable to accompany the act of propeller feathering with dilution of the lubricant system. Since dilution entails a diversion of oil flow from the main tank to the hopper, the feathering reservoir 32 and supply line 34 will be positively and quickly re-filled with diluted oil. To effect a concomitant action of propellerl feathering and dilution the separate switches controlling the Vfeathering pump 31 and the dilution solenoid 88 may be closed at or about the same time. Alternatively, and perhaps preferably, the switch controlling feathering pump 31 may be arranged to close and open a circuit through dilution solenoid 88 as a part of the same operations starting and stopping the feathering pump.

According to the operation of the system, in an aircraft which has been in llight for a considerable length of time the oil in the engine lubrication system is heated to the maximum value set by the oil temperature regulator, and is substantially free of diluent. The position of the sequence valve controlling flow to the oil tank is, under these conditions, substantially that shown in Fig. 5. As there illustrated, the port 65 is fully closed and the port 64 is fully opened. Therefore, substantially all the oil returned 'from the engine is directed to tank inlet 24 and from there passes to manifold 39 and along the assembly of batlles 42 and 44 where it is deaerated and to some extent cooled. The head pressure of the oil in the main tank is at this time suicient to overcome the resistance ofthe weighted flapper valves 48 so that the oil' may' pass from.. the. tank through ports 41 intothe lower part of hopper 21 and-out outlet 25120 conduit i5' by which2 it.-is-returned to .the engine. As the aircraft comes in to land, or

-ly described, and, in owing through the ports and passages leading to chamber Si., intimately contacts and cools the valve body 68, the. body being more responsive to the diluent'temperature than to the oil temperature since it is shielded from direct contact with the oil by the hood 85'.. In

response to the cooling effect soobtained the valve assembly moves to close off port fi and' openport 65. The oil ow accordingly isY diverted from tank inlet 24 to tank inetv 25` and passes to the hopper 21, having mixed therewith diluent which isA supplied continuously to the system as .long as switch 9'3 remains closed.` The engine is'c'ontin -uedin operation, circulating oil through the en -gine and through theV hopper 21 of the tank until the desired dilution percentage has been attained, this being. determined empirically or by appropriateV measuring devices. As the-oil: circulates during dilution its'clensitv gradually becomes less so that the. oil owing through the hopper 2.1 has a lower density than the substantially un- .diluted oil in the tank4 outside the hopper; However, noy ow of undiluted oil from themain tank into the system is permitted since the weighted fiapper valves 48 hold' the ports 441- closed against all but a determined. difference in head pressure between the main tank and the hopper. When ,the desired dilution percentage is reached the dilution control switch 93 is'opened. tointerrupt the now of diluent to the lubrication system, andthe engine is stopped. There is now present` within the engine and within all the. lines of the lubrication. system, includ-ing the propeller teathering supply line 35 and excepting the main tank, highly diluted oil which effectively resists congelation during the period in which the aircraft stands idle.

When the engine. is next. started, preparatory .to night, the lubricating oil. in the engineV andin the system including. hopper 21` of the tank, -although not congealed isf cold. Further, in the .casef of the sequence valve assembly the thermal substance 'i9 has responded, to low temperature moving the valve 65 to closed. position. and the valve. Ell-to opened position. Therefore, when. the engine is started the oil flowing` to the tank nds port 64 closed and. is compelledto pass through port 65 and follow the short path through the tank dened by hopper 21. Continued operation of the engine warms the oil, and one eii'ect of such gradually increasingv temperature is to heat the hopper 21v and eiTect by a process of heat conduction warming of the adjacent oil in the main tank. The hopper 21 may in this sense be described as a warm-up compartment. Another result of higher oil temperature is to effect vthrough expansion of the thermal substance 19 in valve bodyl iid motion oi' the body to open port t.. When this occurs, some-of the warm-oil from the engine iows to the manifold 33 in the main and begins a washing out or expelling ofthe 'cold oil therein. It -will be understood that the manifoid 39 and its sup-ply conduit 3S.v have been 4kept clear 'of' 'congealed oil by thel admission of diluent through portiS-T in valve; 66. In order to provide.- forimmediate ow' through the main 'tankl there is provided. inthe bales 42, it` and 461 respective openings'99, lul and |02 adjacent Athe'hopper 21.v These openings provide a short circuit through the warmest part of thev tank which is that area' adjacent hopper 21 and estab- '.lish a. quick ow conducive to a rapid condition.-

'ing ot all the oil. in the tank for free ow. AS

ithe oil temperature rises still higher, and approachesl the limit. set bythe oil cooler 2l, valve 6.1 closes port' 65 whereupon all theA oil is required .to pass through the'. main tank.

4viscosity highly resistant to motion in the engine.

In order to. attain the ldesired low 'viscosity it is 'often necessary to 'add thirty to fortyv percent diluent vby volume to the warm-up or hopper system. Such a largeV proportion of highly vola- 'tile and'low-'viscosityliquid may have a, harmful veiect in the system if the subsequent engine warm-up is su'iciently rapid to heat` theoil to a stillv lower viscosity before a substantial amount oithe diluentv has evaporated from the system. One disadvantage is thatwhen the engine' is operated at very high speed during warm-up, the -lowered viscosity of the oil mayv providev inadequate lubrication for the engine. Another dis- Yadvantage results from a tendencyfor the diluted oil tov acquire a high state of turbulence on discharge into the oiI tank resulting in a loss of oil by eiiervescent boiling 0r spewingy from the Vents and breathers.

Using for purposes of illustration a typical embodiment of the present oil tank and system in an aircraft it will be described how viscosity control ofthe oil is achieved in a manner preventing spewingv and in a, manner holdingl the oilviscosity from falling below a predetermined safe level. Assuming that the lubricant has been diluted so that it consists of about thirty per cent diluent, and that the engine has been allowed -to stand in a sub-zero temperature overnight, the diluted oil in the engine will be cold" but will move in response to cranking of the engine and allow the engine to start. Rapid warm-upand continued running of the engine requires that an engine speed of 1000 to 1200 R. P. M. be maintained. Operation of the engine heats the oil, and thestemperature thereof rises quickly, reaching a value of approximately 160 E. attire engine inlet. in eight to twelve minutes. At i'lrst, as the-oil'temperature rises the oil viscosity will drop steadily until a temperature: of about F. is reached. This is temperature outof the engine andv probably is reached iveY to seven m-inutes after the engine is started. Above a temperature of 9U" some of the diluent in the oil vaporizes and leaves the lubrication system through ythe ventsV in the oil tank. As the oil temperature continues to rise the rate ofvaporization of` diluent increases' rapidly, and,l in the absenceof controls for preventing such condition will bring about violent boiling in. the tank hopper '2-1 re.- sulting in. loss of oil, and possible engine failure since. the main oil supply in. thetank' may not be yet conditioned for flow to replace the oil lost overboard. According to the present' system, however, when the temperature of the oil returning from the engine reachesapproximately l30 F. the sequence valve assembly at the tank begins to open ow to :tank inlet 24, permitting Warm oil to pass into the main body of the tank. By this means, and as a result of the warming action obtained through the wall of hopper 21, the short circuit through baffle openings 99, and |02 is opened. The oil and diluent mixture that is delivered to the tank thus displaces liquid undiluted oil around the hopper 21 which ows into the bottom of hopper 21 where it mixes with the still highly diluted oil in the hopper to supply to suction line l a cooler more viscous liquid than is returned to the tank from the engine. The tendency is to stabilize the viscosity of the mixture flowing into the engine at a level safely above the critical value of lubricating efliciency. Accordingly, due to the loss of diluent by vaporization and the mixture of cool undiluted oil with hot diluted oil, the oil viscosity is held from dropping below a predetermined low value until the oil out of engine temperature passes 130 F. whereupon the oil viscosity rises, since above 130 evaporation is more rapid and a larger proportion of undiluted oil is drawn from the main supply. The conditions obtaining in the lubrication system at this point are that something less than the added volume of diluent is mixed with about two-thirds the total oil supply rather than with only one-eighth or less of that supply which is represented by the volume in the warm-up hopper system, substantially all of the remaining diluent being held in the tank at a temperature which will not produce violent boiling or too rapid vaporization. This means that only a small quantity of diluent is taken into the engine and this can easily be discharged as vapor.

The tank sequence valve provides to a large degree a uniform oil temperature rise during warmup to the operating temperature set by the oil cooler. Heretofore in oil systems with very large oil tanks temperature surges have frequently been observed caused by the fluctuation of flow from hopper to tank and back. The gradual temperature effect of the present tank sequence valve inhibits or modulates temperature surge conditions. oil system, as indicated by the cock pit engine oil temperature gauge, may be slower than conventional systems, but complete warm-up of the tank is always assured without engine oil temperature fluctuations. It will be observed that the present system contemplates a complete thawing out and utilization of all the oil in the system. In oil tanks of the prior art, particularly those having only a single flow path, namely through the hopper, a large quantity of the main oil supply in the tank is slow to thaw, remaining as a congealed mass in the tank.

According to a modification of the invention it is proposed that as a part of the same action initiating dilution in the system a Valve controlling flow through the oil cooler be closed to compel fiow through the cooler rather than in by-passing relationship thereto. ",[n this manner it may be insured that during dilution the oil temperature will not rise above the level set by the cooler and as a consequence the viscosity of the oil and diluent mixture will not drop below the value of lubrication efliciency. Referring to Figs. 8 and 9, the oil cooler, here indicated at |03, has mounted thereon a valve body |04 containing inlet and outlet ports |05 and |06 connected respectively to the engine scavenge pump' and to the oil tank. The valve body |04 is The warm-up of the entire nur formed with an internal chamber |01 communieating with inlet 4|05 and a chamber |08 communicating with outlet |06. Another chamber |09 in the valve body communicates with the heat exchange portion of the cooler, including a series of vertical oil conduits ||0 and transversely disposed core of air flow tubes A port ||2 connects inlet chamber |01 and chamber |09, and oil flowing through the port |2 may enter conduits ||0 where it is directed to a header chamber ||3 from which it may return through the core around the air flow tubes to a chamber ||4 in the valve body |04 and flow past a check valve ||5 to chamber |08 and the outlet |06. Inlet chamber |01 is directly connected to outlet chamber |08 by a port H6, so that the oil entering body |04, may, instead of passing through'port ||2 to the heat exchange portion of the cooler, be lay-passed directly to the outlet. A thermostatically controlled valve assembly, comprising a valve I |1 controlling port ||2 and a valve ||8 controlling port IIB, is positioned in chamber |01. A thermostat, indicated generally at ||9 is disposed between the valves ||1 and ||8 and operates when the oil is cold to permit by-passing flow thereof through port IB and operates when the oilis hot to close the by-pass ||6 and compel flow through port ||2. After passing through port ||2 the oil is directed to conduits ||0, and, in the event its temperature still is not such as to require cooling, may ow alternatively through a port |2| in body |04 to chamber ||4 and past check valve ||5 to the outlet. The port |2| is controlled by a valve |22 forming part of an assembly including a thermostat |23 arranged in chamber ||4 in the path of flow to the outlet. The valve |22 normally is open but'as the oil flowing thereby rises in temperature the thermostat |23 responds, moving valve |22 to close port |2| thereby requiring the oil to flow to the heat exchange portion of the cooler and be cooled.

According to the present invention the assembly comprising valve |22 and thermostat |23 is modified to include a heating coil |24 arranged adjacent the thermostat |23. As shown yin Fig. 8, the heating coil |24 is arranged in an electrical circuit including positive and negative leads |25 and |26, a battery |21 and a switch |28. In series with the coil |24 in the circuit is the dilution control solenoid here indicated at |29. According to the arrangement of the parts, when the switch |28 is closed a circuit is completed through the coil |24 and through the solenoid |29 in such manner that the coil is heated to Warm the thermostat |23 and the solenoid |29 is energized Ato admitrdiluent to the lubrication system. Warming of the thermostat y|23 results in closing the valve |22, irrespective said valve means for motion of said hopper valve through and beyond the inlet associated with 13 sean'hopperinresponse' to -eroessivapressurecori.-r 'd'itiens at said inlet; l

2.- In an engine' lubrication system', the come` bination of an oil tank; means defining@ first v and Y' second oil flow pathsthrough said tank, sepa-v rate inlets to' saidpaths, valves respectively con? trolling'- how through said inlets, a thermostat i exposed to thel oil returning tothe tank and' cuoeratingr said valves in response to variations inoil temperature, said valves actingto open said g first path through the tank and to close said see",- ond path when the oil temperaturev isbelowa predetermined value-and acting to close said nrst path and to open said second path when the oil f second' p'ath the ol'osedposition' ofi said valve.

3; In an engine? lubrication system, the comhinationofan oil` tank, means defining rst' and second oil' now" paths through said tank; the oil being directed alternatively through said paths, a common outlet from the tank for said ilow paths, means foradding' a' dil'uent to' the oilin the" system, means forv causing. the oil: flow to followsaid nrst path through the tankA during addi"- tion ofj the dilu'ent; the` oil in said second path remaining" substantially'` undiluted' and therefore more densethan: the oil in said nrst: path, and valve means forA inhibiting` the now of thev oir in said' second path toA said" outlet tendingl to take place by reasonofthediherence in densityof the oils in said paths.

4. In an engine lubrication system', the combination of" an oil tank having rst and second compartments, an outlet from thetank' common f to said compartments, said second compartmentcommunicating with said: outletthrough said nrst compartment; control means for directing-the oil ait'ernative'ly` through said compartments in acaoordance withthe temperature thereof; means for' adding a dluent t'o the oil in the system'. the addition of the diuent affecting,v said control means to cause the oil to iiow through said tank by wayofv said 'rst compartment irrespective oi!y the temperature thereof, and' pressure*resp'cmsi've` valve means between said'v first and'. second' comel pertinents inhibiting mixture of the'moredense,

oil in said second compartment with the diluted oil inrsaid first compartment.

5. In an engine lubrication system, the. come bination of an oilv tank, means dehing instand second' oil now paths through said tank an oil control body having' separated chambers constituting respectively the inlets to said rst and second flow paths, the oil returning to the tank entering saidl body and passing. therefrom the tank alternatively through said separated chambers,t a valve assembly controlling. flow through said'l chambers, a thermostat responsive tof the temperature ofthe oil entering saldi hody land initiating motion ofl said valve assembly to. open How to said rst path during. a predetermined range of oil temperatures and to open. flow togsaid second path during another and higherrange of oil temperatures.. means for addingA a. diluet to .the system by way of" said' oil control'.b1adzar1dv a path of entry for said diluent. including. a shield aboutV said thermostat bringing' flowing. diluent into Contact with said tnerrriostat to the. exc-iusion of the oil" whereby said thermostat is caused I4 tiov1 initiate.- motloni of? said" valveu assemhlyto-open ii'oiv to said; rsty path irrespective of thaoil temperature... i f

6. Im an; enginev lubrication system, including asupply tank; having: nrst: anda second flow' paths tiierethrough;Y means for directing the lubricant returning from the engine'. through the tank alternatively loywaly` ofi saidrstfand seconmpathzt s'aidmeans-1 including.' ai thermostat in the path of? the returning oil, means for adding ai diluent to# the system, said' diluent ilovvin'gP to` the: system by way1 oi said therrnostat,p and afshieldi in: the path of the returning oil: ahead! of: they thermo:t stat and` protesting said. thermostat; from direct 5 contact with` theoil and enforcing an'. iiuiimatel contact of the diluentiwith thejthermostat...

7. In an engine lubrication system', including a supply tankv 'having' rst and. second flow paths therethrough meanse forv directing the lubricant through the tank alternativelybyiway of said irsti and second paths, said: means including. a thermostat in the path of the oil' and operative in responsetoa rising oil` temperature to divert theoi'l flow from said rst" path to said second path; means for' adding a diluent tothe system,

said-vdiluent owingto the system by way"of"said thermostat, and a shield inthe path of the. oil

oi" thermostat rendering said. thermostat more* sensitive to the cooling efiect of the dlluentthan tev the heating effect ofV the "oil whereby' addition of: thediluent is' accompanied by diversion-of the oil flow-'from said second' path tosaid' lrst path.

S In an eng-ine lubrication system, means providing alternative flow paths for theV lubricant, means for controlling'lubricant ow through said paths including a thermostat; means for adding a' diluent tok the system, said diluent passing to the'systenr by way'ofsaid' thermostat, and a shield inthe path' of: the oil' vahead of the thermostat rendering said thermostat more' sensitive' to the temperature of*k the diluent than to the lubricant wherebylubricant ow control during the dilution process is made independent of lubricant temperature.

9. In an engine lubrication system, an oil tank, a first conduit leading from said engine to said and a second. conduit leading from the tank to' the engine, means dividing. said tank into` a, hopper and a main section having a common outlet to said'. second conduit,v a valve' body mounted' on said tank, an inlet Yin said body recen/ing the discharge end' ofA said first conduit, valve means in said body for directing incoming oil atsaidinlet alternatively to said hopper or said main section4 of the. tank or tov divide the flow therebetween,. all, in. accordance .with the. tem'- perature. of the eil', a` source. of dluent,A aA line leading from said' source to said valve body;.saiifi diluent. discharging. into and. mixingv with the incoming oil.at.saidlinleuselectively operable means iorlad'mitting. the d'iluent,` and' continuously open smallv diameter passages between said inlet and said' hopper and. said main section of the tank for permitting a limited How of diluted oil to both portions of the tank irrespective of the position of' said valve means.

I'Ol In. an. engine lubrication system, an oil tank constituting` a reservoir of oil for said. engine, pump and conduit means forl circulating.v the oil between the engine and tank under pressure. means dividing said. tank into a warm-up. compartment and4 main` section; a common outlet for said. main section vand said' compartment through which the oil" Vis'dischargedto the engine, a valve ,body on said tank dening an inlet for o il returning from the engine, first and second chambers in said body communicating respectively with said Awarm-up compartment and said main section of the tank, ports in said body between said inlet and said chambers, a valve assembly in said body comprising valves cooperable with said ports and a thermostat responding to temperature variation to move said valves to positions alternatively opening and closing said ports, and a mounting for said valve assembly enabling a pressure responsive motion thereof in response to iluid'pressure of a predetermined high value in said inlet in a direction to open the port leading to said nrst chamber when said valve assembly is in a position closing said port.

11. In an engine lubrication system, an oil tank, means for circulating oil between the tank and engine, means defining relatively short and long oil flow paths through said tank, valve means mounted on said tank for directing the oil alternatively through said paths, a source of diluent, selectively operable means for admitting diluent to said tank under the control of said valve means, said diluent mixing with the oil entering said tank, a thermostat in the path of the oil entering said tank and in the path of the diluent entering said tank for operating said valve means, and a shield about said thermostat for precluding mixture of iiowing diluent with said oil during iiow past said thermostat.

- 12. In an engine lubrication system, an oil tank, means defining iirst and second ow paths through said tank, a valve body mounted on said tank, anV oil inlet in said body, a pair of outlets respectively in communication with said rst and second flow paths, rst and second ports respectively connecting said inlet with said outlets, valve means in said body responding to a changed condition of the oil for directing incoming oil at said inlet alternatively through said ports, and continuously open passages of small diameter relatively to said ports for admitting a limited flow of oil tov said first and second iiow paths from said inlet irrespective of the position of said valve means.

13. In an engine lubrication system, an oil tank sequence valve comprisingA a body presenting an oil .inlet and a diluent inlet and a pair of outlets, an inlet chamber into which said oil inlet opens, first and second ports respectively connecting said inlet chamber to said outlets, a valve assembly including first and second valves Vrespectively controlling said ports and a thermostatin said inlet chamber for operating said valyes, a hood surrounding saidthermostat and shielding it from direct contact by the o il, discharge openings in said hood, and a passage leading from said diluent inlet to the interior of said hood. 'A 14. An engine lubrication system according to claim 13, characterized in that said'passage in cludes telescoping tubular elements defining a continuation of said diluent inlet to said valve assembly, one of said elements engaging said assembly and moving therewith.

15. In an engine lubrication system, the combination of an oil tank, means defining first and 'second oil flow paths through said tank, an oil flow controlunit, including a body having a chamber receiving oil returning to the tank and `iirst and second oppositely disposed axially aligned ports communicating said chamber respectively with Asaid iirst and second paths, first and second valves in said chamber respectively jfs controlling said first and second ports, a. thermostat interconnecting said valves and responsive to the temperature of the oil in said chamber for operating saidvalves, said valves acting under the control of said thermotsat to direct the oil iiow to said rst path within a predetermined range of low temperature values, to split the oil flow between said paths within a predetermined range of intermediate temperature values, and to direotthe oil flow to said second path within a predetermined range of high temperature values. and by-pass means for permitting at least a restrictedoil ow to said second path in all positions of said valves.

16. In an engine lubrication system. the combination of an oil reservoir comprising a main tank and a hopper within said main tank, outlet means establishing communication between the lower parts of the tank. and hopper, control means for directing the oil alternatively to the main tank and hopper in accordance with the, tem-'- perature thereof, means for adding a diluent to theoil in the system, the addition of the diluent affecting said control means to cause the oil to flow through said reservoir by way of said hopper irrespective of the temperature thereof, and valve means controlling flow from said main tank'through said outlet means. 17. .In an engine lubrication system, the combination of an oil reservoir 'comprising a main tank and a hopper within said main tank, outlet means establishing communication between the lower parts ofthe tank and hopper. control means for directing the oil alternatively to the main tank and hopper, and valve means controlling owfrom the lower part of said main tank through said outlet means. A 18. In an engine. lubricationsystem, the combination of an oil reservoir comprising a main tank and a hopper within said tank, outlet means establishing communication between the lower parts of the tank and hopper, control means for directing the oil alternatively to the main tank and hopper in accordance with a changed condition thereof, means for adding a diluent to the oil in the system, the addition of the diluent affecting said control means to cause the oil to ow through the reservoir by way of said hopper, and valve means controlling flow from the lower part of the maintank through said outlet means to provide for segregation of the diluted and lundiluted oil.

`19. In an engine lubrication system, the combination of an oil cooler having a heat exchange portion and a path in by-passing relation to the heat exchange portion, an oil tank having a short circuit path therethrough, a valve associated with said oil cooler and movable to close and open said Joy-.pass path, another valve movable to open and close said short circuit path through the tank.. means including an electromagnetically operated valve for adding a diluent to the vsystem, an electrical circuit for actuating said electromagnetic valve, means responsive to addition of the diluentl for moving the said other valve to open said short circuit path, and means in se'- rieswith said electromagnetic valve for initiating movement of the iirst said valve t0 close said by-pass path. l 2,0. In an engine lubrication system, the combination of an oil coolerlhaving a heat exchange portion and a path in by-passing relation to said heat exchange portion, a valve movable to open and close said by-pass path, a means for adding a diluent to the system comprising an elec- 17 trical circuit including an electrically actuated solenoid, and means in said electrical circuit and operating in accompaniment with the energizing of said solenoid to initiate movement of said valve to close said by-pass path.

21. In an engine lubrication system, the combination of an oil cooler having` a heat exchange portion and a path in by-passing relation to said heat exchange portion, means for adding a diluent to the system including an electromagnetic m valve, an electrical energizing circuit for said valve, a heating coil in said circuit, a thermostat expansible under the inuence of said heating coil, and a control valve movable by expansion of said thermostat to close said oil cooler by-pass path.

22. An engine lubrication system according to claim 21 having an oil tank with a short circuit path therethrough and a valve and thermostat means movable from a position closing said short circuit path to a position opening said path in response to lowering temperatures, characterized by a path of entry for said diluent bringing it into contact with the valve and thermostat means circuit path through the tank thus being opened 18 and the oil cooler by-pass path being closed conn comitantly with addition of the diluent.

ALLAN C. HOFFMAN. WALTER H. GEDDES. JAMES D. OLCOTT.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 2,107,188 Ryder Feb. 1, 1938 2,245,198 Hunter June 10, 1941 2,311,069 Miller Feb. 16, 1943 2,326,051 Miller Aug. 3, 1943 2,338,483 Beebe Jan. 4, 1944 2,353,577 Magrum July 11, 1944 2,359,448 Shaw Oct. 3, 1944 2,364,119 Anderson Dec. 5, 1944 2,383,878 Miller Aug. 28, 1945 2,408,265 Miller Sept. 24, 1946 2,419,630 Cruzan Aug. 29, 1947 2,436,513 Hostetter Feb. 24, 1948 2,449,696 Geddes Sept. 21, 1948 2,483,448 Weitzen Oct. 4, 1949 

